In the processing and packaging of semiconductor devices, wire bonding (e.g., ball bonding, wedge bonding, etc.) continues to be a widely used method of providing electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). More specifically, using a wire bonder (also known as a wire bonding machine) wire loops are formed between respective locations to be electrically interconnected.
An exemplary conventional wire bonding sequence (using ball bonding techniques) includes: (1) forming a free air ball on an end of a wire extending from a bonding tool; (2) forming a first bond on a die pad of a semiconductor die using the free air ball; (3) extending a length of wire in a desired shape between the die pad and a lead of a leadframe; (4) stitch bonding the wire to the lead of the leadframe; and (5) severing the wire. In forming the bonds between (a) the ends of the wire loop and (b) the bond site (e.g., a die pad, a lead, etc.) varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy, amongst others.
In connection with wire bonding, it is often desirable to confirm that a portion of wire is properly bonded to a bonding location. Wire bonding machines marketed by Kulicke and Soffa Industries, Inc. often utilize a “BITS” process (i.e., Bond Integrity Test System) to confirm that proper wire bonds have been formed. Exemplary details of such processes is disclosed in International Patent Application Publication WO 2009/002345 which is incorporated by reference herein in its entirety.
Thus, it would be desirable to provide improved methods of determining whether a portion of wire (e.g., a portion of a wire loop) is properly bonded to a bonding location.